 (s/defn do-probability :- s/Bool
   "'rand is inclusive of 0 and exclusive of 1, so our test should not have '=."
   [cutoff :- ProbabilitySchema]
-  (< (rand) cutoff))
+  (< (*rand*) cutoff))
 
 (s/defn forward-subscription :- [MessageEnvelopeSchema]
   "Take a node's 'downstream map and a new 'subscription.

  (if (empty? downstream)
    []
    [[:message-envelope
      (rand-nth (seq downstream))
      :forwarded-subscription
      subscription
      (get-envelope-id)]]))


    ;; Forward subscription to :downstream.
    (let [downstream (seq downstream)
          downstream+ (reduce (fn [x _] (conj x (rand-nth* downstream)))
                              downstream
                              (range (:connection-redundancy config)))]
      (map
